It has been a serious problem for truck operators to maintain the size (required by law) of the protective wheel flaps behind the truck wheels of dump trucks. The problem arises when the dump body is raised into dumping position thus projecting the wheel flaps (mounted at the rear end of the dump body) downwardly into engagement with the rear wheels of the truck, which causes damage to the flaps. When the wheel flaps come in contact with the wheels, they are frequently broken off or bent and as a result the truck operators, for the most part, drive without the required wheel flaps and subject themselves to the penalties prescribed by the law when caught. The present invention provides a solution to this problem by mounting the wheel flaps on slides so that they may be retracted inwardly and out of contact with the wheels so that they may be free to swing forwardly under the truck as the dump body is elevated into dumping position.